Fix: notify locale on request review merge request email
What does this MR do and why?
Reason
Right now the email template for request review merge request_email notification can only be sent in English
Result
in this MR I updated the template with i18n enabled strings instead of hardcoded strings. After this MR it will be able to send languages the user prefers.
How to test locally
- Start your GDK instance locally or via gitpod or other ways
- Open the browser with your instance with path gdk/rails/mailers/notify/request_review_merge_request_email
- Observe.
/cc @prajnamas @orozot @qk44077907 @JeremyWuuuuu
Screenshots or screen recordings
MR acceptance checklist
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Edited  by qt
